Evaluation of greenhouse gas emission and reduction potential of high-food-waste-content municipal solid waste landfills: A case study of a landfill in the east of China.

This study proposes a comprehensive evaluation method based on a two-stage model to assess greenhouse gas (GHG) emissions and reductions in high-food-waste-content (HFWC) municipal solid waste (MSW) landfills. The proposed method considers typical processes such as fugitive landfill gas (LFG), LFG collection, flaring, power generation, and leachate treatment. A case study of an HFWC MSW landfill in eastern China is considered to illustrate the evaluation. The findings revealed that the GHG emissions equivalent of the case landfill amounted to 21.23 million tons from 2007 to 2022, averaging 1.03 tons CO2-eq per ton of MSW. There was a potential underestimation of LFG generation at the landfill site during the initial stages, which led to delayed LFG collection and substantial fugitive LFG emissions. Additionally, the time distribution of GHG emissions from HFWC MSW was significantly different from that of low-food-waste-content (LFWC) MSW landfills, with peak emissions occurring much earlier. Owing to the rapid degradation characteristics of HFWC MSW, the cumulative LFG production of the landfill by 2022 (2 years after the final cover) was projected to reach 77 % of the total LFG potential. In contrast, it would take until 2030 for LFWC MSW landfills to reach this level. Furthermore, various scenarios were analyzed, in which if the rapid LFG generation characteristics of HFWC MSW are known in advance, and relevant facilities are constructed ahead of time, the collection efficiency can be improved from 31 % to over 78 %, resulting in less GHG emissions.

Using a combination of δ13CDIC-DOC-difference in dissolved inorganic and organic carbon, δ2H, and δ18O to localize leachate leaks at landfill sites in China.

The investigation of leachate leakage at numerous landfill sites is urgently needed. This study presents an exploration of environmental tracing methods using δ2H and δ13C-difference in dissolved carbon (δ13CDIC-DOC) to localize leachate leak points at landfill sites. δ2H, δ13CDIC, δ13CDOC, δ18O, and an array of physicochemical indices (e.g., total dissolved solids, temperature, and oxidation reduction potential) were monitored in both leachate and groundwater from different zones of a landfill site in China during the year of 2021-2023. Moreover, data for these parameters (i.e., the isotopic composition and physicochemical indices) from twelve published landfill cases were also collected, and these groundwater/leachate data points were located within 1 km away from the landfill boundary. Then statistical analyses, such as Pearson correlation analysis and redundancy analysis (RDA), were performed using both the detected and collected parameters at landfill sites. Consequently, the intensity of interaction between leachate and background groundwater was found to significantly control the isotopic fractionation features of hydrogen and carbon, and both the content of major contamination indicators (total dissolved solids, chemical oxygen demand, and ammoniacal nitrogen) and the oxidation reduction potential were the key impact factors. Accordingly, the water type used to indicate leachate leakage points was determined to be leachate that significantly interacted with the background groundwater or precipitation (LBGP). δ2H showed a perfect linear correlation (0.81 ≤ r2 < 1.0) with δ13CDIC-DOC in leachate under highly anaerobic landfill conditions, and the δ2H & δ13CDIC-DOC combinations in the LBGP were significantly different from those in the other water types. For groundwater with total dissolved solids lower than 1400 mg/L at landfill sites, a strong positive linear correlation (r = 0.83) was revealed between δ13CDIC and δ13CDOC. Based on these insights, δ2H versus δ13CDIC-DOC plots and RDA using δ2H and δ13CDIC-DOC as response variables were proposed to localize leak points at both lined landfills and leachate facilities. These findings further understanding of the isotopic fractionation features of hydrogen, carbon, and oxygen and provide novel environmental tracer methods for investigating leachate leak points at MSW landfill sites.

AI-Driven Sensing Technology: Review.

Machine learning and deep learning technologies are rapidly advancing the capabilities of sensing technologies, bringing about significant improvements in accuracy, sensitivity, and adaptability. These advancements are making a notable impact across a broad spectrum of fields, including industrial automation, robotics, biomedical engineering, and civil infrastructure monitoring. The core of this transformative shift lies in the integration of artificial intelligence (AI) with sensor technology, focusing on the development of efficient algorithms that drive both device performance enhancements and novel applications in various biomedical and engineering fields. This review delves into the fusion of ML/DL algorithms with sensor technologies, shedding light on their profound impact on sensor design, calibration and compensation, object recognition, and behavior prediction. Through a series of exemplary applications, the review showcases the potential of AI algorithms to significantly upgrade sensor functionalities and widen their application range. Moreover, it addresses the challenges encountered in exploiting these technologies for sensing applications and offers insights into future trends and potential advancements.

Molecular Dynamics Simulation of the Interaction within the Carboxymethyl Cellulose-Modified Montmorillonite Lamellae at Aggressive CuCl2 Concentrations.

To elucidate the degradation mechanism of the CMC-modified MMT composite at aggressive Cu2+ concentrations, large scale molecular dynamics simulation was conducted for CuCl2 concentrations ranging from 0 to 800 mM. Both CMC and MMT followed the Langmuir isotherm for Cu2+ adsorption, and the adsorption capacity of CMC (8.75 mmol/g) was much higher than that of MMT (0.83 mmol/g). Despite the CMC mass ratio being only 4.1%, it adsorbed up to 34.3% of the total adsorbed Cu2+. The Cu2+ attraction ability hierarchy of oxygen-containing functional groups in the CMC is as follows: carboxylic oxygens > alcoholic oxygens > carbinolic oxygens > bridging oxygens > glucose oxygens. Carboxyls were the most effective in chelating and complexing with Cu2+, and they could be intentionally added in artificially synthesized polymer-MMT composites for Cu2+ containment. Formation of the Cu2+ cation bridge between CMC and MMT at aggressive CuCl2 concentrations contributed to the transition of CMC density distribution from unimodality to bimodality and enhanced resistance of polymer elution. As the CuCl2 concentration increased, the stoichiometric ratio between the chelated Cu2+ and carboxylic oxygens increased from 1:2 to 1:1, suggesting the evolution of the Cu2+ chelation mechanism.

Numerical investigation and optimal design of capillary barrier cover with passive gas collection pipes on the performance at limiting landfill gas emissions.

Relying solely on soil properties may not fully ensure the performance of capillary barrier covers at limiting landfill gas (LFG) emissions. This study proposed to install passive gas collection pipes in the coarse-grained soil layers of capillary barrier covers to enhance their performance at limiting LFG emissions. First, the LFG generation rate of municipal solid waste and its influencing factors were analyzed based on empirical formulas. This information provided necessary bottom boundary conditions for the analyses of LFG transport through capillary barrier covers with passive gas collection pipes (CBCPPs). Then, numerical simulations were conducted to investigate the LFG transport properties through CBCPPs and reveal relevant influencing factors. Finally, practical suggestions were proposed to optimize the design of CBCPPs. The results indicated that the maximum whole-site LFG generation rate occurred at the end of landfilling operation. The gas collection efficiency (E) of CBCPPs was mainly controlled by the ratio of the intrinsic permeability between the coarse- and fine-grained soil (K2/K1) and the laying spacing between gas collection pipes (D). E increased as K2/K1 increased but decreased as D increased. An empirical expression for estimating E based on K2/K1 and D was proposed. In practice, CBCPPs were supposed to be constructed once the landfilling operation finished. It is best to select the fine- and coarse-grained soils with K2/K1 exceeding 10,000 to construct CBCPPs.

Negative mixing enthalpy solid solutions deliver high strength and ductility.

Body-centred cubic refractory multi-principal element alloys (MPEAs), with several refractory metal elements as constituents and featuring a yield strength greater than one gigapascal, are promising materials to meet the demands of aggressive structural applications1-6. Their low-to-no tensile ductility at room temperature, however, limits their processability and scaled-up application7-10. Here we present a HfNbTiVAl10 alloy that shows remarkable tensile ductility (roughly 20%) and ultrahigh yield strength (roughly 1,390 megapascals). Notably, these are among the best synergies compared with other related alloys. Such superb synergies derive from the addition of aluminium to the HfNbTiV alloy, resulting in a negative mixing enthalpy solid solution, which promotes strength and favours the formation of hierarchical chemical fluctuations (HCFs). The HCFs span many length scales, ranging from submicrometre to atomic scale, and create a high density of diffusive boundaries that act as effective barriers for dislocation motion. Consequently, versatile dislocation configurations are sequentially stimulated, enabling the alloy to accommodate plastic deformation while fostering substantial interactions that give rise to two unusual strain-hardening rate upturns. Thus, plastic instability is significantly delayed, which expands the plastic regime as ultralarge tensile ductility. This study provides valuable insights into achieving a synergistic combination of ultrahigh strength and large tensile ductility in MPEAs.

Periodic injection of liquefied kitchen and food waste in municipal solid waste: Effects on leachate and gas generation.

With continuous advancements in the zero-waste strategy in China, transportation of fresh municipal solid waste to landfills has ceased in most first-tier cities. Consequently, the production of landfill gas has sharply declined because the supply of organic matter has decreased, rendering power generation facilities idle. However, by incorporating liquefied kitchen and food waste (LKFW), sustainable methane production can be achieved while consuming organic wastewater. In this study, LKFW and water (as a control group) were periodically injected into high and low organic wastes, respectively. The biochemical characteristics of the resulting gas and leachate were analyzed. LKFW used in this research generated 19.5-37.6 L of methane per liter in the post-methane production phase, highlighting the effectiveness of LKFW injection in enhancing the methane-producing capacity of the system. The release of H2S was prominent during both the rapid and post-methane production phases, whereas that of NH3 was prominent in the post-methane production phase. As injection continued, the concentrations of chemical oxygen demand, 5-d biological oxygen demand, total organic carbon, ammonia nitrogen, total nitrogen, and oil in the output leachate decreased and eventually reached levels comparable to those in the water injection cases. After nine rounds of injections, the biologically degradable matter of the two LKFW-injected wastes decreased by 8.2 % and 15.1 %, respectively. This study sheds light on determining the organic load, controlling odor, and assessing the biochemical characteristics of leachate during LKFW injection.

CFD-DEM study on transport and retention behaviors of nZVI-clay colloids in porous media.

Transportation process of nano scale zero valent iron (nZVI) in clay-rich soils is complicated and crucial for in-situ remediation of contaminated sites. A coupled computational fluid dynamic and discrete element method (CFD-DEM) was used to investigate the interplays of repulsive and attractive forces and the injection velocity of this process. The screened Coulomb's law was used to represent the electrostatic interaction, and surface energy density was introduced to represent the effects of the van der Waals interaction. A phase diagram was constructed to describe the interplay between injection velocity and repulsive force (in terms of charge of colloids). Under the boundary and initial conditions in this study, clogging formed at low repulsive force (colloidal charge = -1 ×10-15 C), where increment of injection velocity (from 0.002 m/s to 0.02 m/s) cannot prevent clogging, as in the case of bare nZVI transportation with limited mobility; On the other hand, excessive repulsive force (charge = -4 ×10-14 C) is detrimental to nZVI-clay transportation due to repulsion from the concentrated colloids in pore throats, a phenomenon as in the overuse of stabilizers and was defined as the "membrane repulsion effect" in this study. At moderate charge (-1 ×10-14 C), injection velocity increment induced clogging due to aggregates formed at the windward of cylinder and accumulated at the pore throats.

Monitoring the remediation of groundwater polluted by MSW landfill leachates by activated carbon and zeolite with spectral induced polarization technique.

The municipal solid waste (MSW) landfill in Hangzhou, China utilized zeolite and activated carbon (AC) as permeable reactive barrier (PRB) fill materials to remediate groundwater contaminated with MSW leachates containing ammonium, chemical oxygen demand (COD), and heavy metals. The spectral induced polarization (SIP) technique was chosen for monitoring the PRB because of its sensitivity to pore fluid chemistry and mineral-fluid interface composition. During the experiment, authentic groundwater collected from the landfill site was used to permeate two columns filled with zeolite and AC, and the SIP responses were measured at the inlet and outlet over a frequency range of 0.01-1000 Hz. The results showed that zeolite had a higher adsorption capacity for COD (7.08 mg/g) and ammonium (9.15 mg/g) compared to AC (COD: 2.75 mg/g, ammonium: 1.68 mg/g). Cation exchange was found to be the mechanism of ammonium adsorption for both zeolite and AC, while FTIR results indicated that π-complexation, π-π interaction, and electrostatic attraction were the main mechanisms of COD adsorption. The Cole-Cole model was used to fit the SIP responses and determine the relaxation time (τ) and normalized chargeability (mn). The calculated characteristic diameters of zeolite and AC based on the Schwarz equation and relaxation time (τ) matched the pore sizes observed from SEM and MIP, providing valuable information on contaminant distribution. The mn of zeolite was positively linear with adsorbed ammonium (R2 = 0.9074) and COD (R2 = 0.8877), while the mn of AC was negatively linear with adsorbed ammonium (R2 = 0.8192) and COD (R2 = 0.7916), suggesting that mn could serve as a surrogate for contaminant saturation. The laboratory-based real-time non-invasive SIP results showed good performance in monitoring saturation and provide a strong foundation for future field PRB monitoring.

Successful treatment of peritoneal dialysis for two patients with refractory nephrotic syndrome and acute kidney injury: a case report.

Two patients with refractory nephrotic syndrome were treated with peritoneal dialysis (PD) for diuretic resistance, anasarca and acute kidney injury. Following PD, their fluid overload was promptly alleviated, accompanied by an increase in urine volume and an improvement in renal function. PD as an adjuvant approach enabled them to resume corticosteroids and immunosuppressive agents. Eventually, both patients could be withdrawn from PD and achieved remission of proteinuria.